35Cl Solid-State NMR and Computational Study of Chlorine Halogen Bond Donors in Single-Component Crystalline Chloronitriles

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• 作者：Patrick M. J. Szell ; David L. Bryce
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：May 26, 2016
• 年：2016
• 卷：120
• 期：20
• 页码：11121-11130
• 全文大小：490K
• 年卷期：0
• ISSN：1932-7455

文摘

Halogen bonding is a noncovalent interaction between the electrophilic region of a halogen (σ-hole) and an electron donor, which has gained popularity in the field of crystal engineering due to its strength and linearity. Here, we present a ³⁵Cl solid-state NMR study of chlorine atoms as halogen bond donors, with interpretation aided by crystallographic symmetry and computational chemistry. In a series of chlorinated benzonitrile compounds, the magnitude of the ³⁵Cl quadrupolar coupling constant (C_Q) was found to increase, and the quadrupolar asymmetry parameter (η) was found to decrease upon halogen bonding. A natural localized molecular orbital (NLMO) analysis attributes these changes to an increase in the contribution from the lone pair NLMOs to |C_Q|. This is distinguished from a short proton-chlorine contact, which causes an increase in the magnitude of the σ-bond contribution and a decrease in the lone pair contribution, resulting in an overall decrease in |C_Q|. This first direct ³⁵Cl solid-state NMR study of chlorine as a halogen bond donor provides new physical insight into the relationship between NMR observables and the halogen bond.